In some circumstances, representations of credentials to be matched are exchanged in cleartext and compared with a cleartext repository of matches worth noticing. However, such a solution may not protect the confidentiality of the exchanged information. The complete information about the respective credentials of the peering entities may be disclosed although there is only an interest in matching combinations regardless of the particular nature or content of that combination. Encryption may provide a partial answer to this existing problem. Exchanging the credentials to be matched in an encrypted form, using a secure encryption scheme and predistributing an encrypted representation of each critical matching to each entity, may allow it to match a combination without knowing the real nature of the property. However, although this may solve the confidentiality issue, it still leaves another open problem. It allows, for example, an eavesdropper to trace entities with similar properties since the exchanged values are always the same. Some of the solutions in literature solve this issue by providing a sufficient number of pseudonyms and a trapdoor function to verify that these pseudonyms are in fact legitimate ones. The main drawback of these schemes may be that they depend on a central entity for the provision of multiple pseudonyms.